[j-nsp] policing TCP traffic

[Jason Parsons]

Bob,

Some more detail on my policing concerns; hope you can offer some more 
help.

To make things a little easier, I applied the policer directly to the 
interface:

     fe-0/0/3 {
         unit 0 {
             family inet {
                 policer {
                     input policer-1;
                 }
                 address 192.168.11.2/24;
             }
         }
     }

I then tried playing around with the settings of policer-1.

     policer policer-1 {
         if-exceeding {
             bandwidth-limit 15m;
             burst-size-limit 15k;
         }
         then discard;
     }

Here's a summary of different bandwidth-limits with different 
burst-size-limits, and the TCP throughput I was able to achieve under 
that configuration:

bandwidth-limit			burst-size-limit			Actual TCP throughput
15M					15k	(10xMTU)			440Kb/s
15M					3m					7.38Mb/s
15M					7m					7.60Mb/s
15M					15m					7.45Mb/s
					(15m = bandwidth(15m) x allowable time for burst traffic (1ms))
15M					30m					7.44Mb/s

30M					15k					12.61Mb/s
30M					15m					27.10Mb/s
30M					30m					26.99Mb/s

As the table shows, the best performance I can get out of a 15M filter 
is about 51% of the configured limit.  However, I can get 90% out of a 
30M filter with a similar configuration.

So, what am I missing?  I know that my testing setup isn't great, but I 
can't find a good explanation for the discrepancy between the 15M and 
30M results.

Thanks again.
  - Jason Parsons

On Friday, Aug 30, 2002, at 19:33 US/Eastern, Robert O'Hara wrote:

> To some extent, I am theorizing, because I am not in front of your
> test setup, but....  as noted, I think the burst-limit is set too high.